Typically, a miniature current transformer consists of a bobbin for mounting the primary and secondary windings, the windings themselves, and standard core inserts. Frequently, the primary winding has many fewer turns than the secondary winding and must handle substantially more current. The primary usually is made of a heavier gage wire.
This construction typically results in a bobbin with an irregular, as opposed to a substantially flat, winding surface. A large proportion of the assembly equipment which automates the manufacture of printed circuit board ("PCB") assemblies rely on vacuum picked heads to acquire and place the PCB components. However, the vacuum heads do not function well in picking up irregular surfaces.
In the prior art, adapting miniature transformer structures to vacuum pickup has involved adding flat, electrically non-functional pickup surfaces to the transformer structure. These additions, however, have increased the material costs and have complicated the soldering steps.